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The role of Amazon fires in the record atmospheric CO₂ growth in 2024

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164 points bikenaga | 9 comments | 27 Sep 25 15:02 UTC | HN request time: 0.303s | source | bottom
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htamas ◴[27 Sep 25 21:02 UTC] No.45399285[source]▶
The Amazon forest is unique in many ways but most importantly because unlike other forests, it CANNOT grow back. The reason for this is that it is a leftover from when the planet was covered in rainforests because it was a lot warmer and wetter in the Eocene epoch. The forest is sustained by the rain it creates from itself. Once the trees are gone, the water will be gone. [1] We also have reasons to think this self-sustaining climate is going to collapse soon [2]

So far the best way to protect it I have found is through the Rainforest Trust [3] which is a foundation that's trying to purchase and protect parts of the rainforests that companies would otherwise cut or burn down for agricultural use.

[1]https://youtu.be/hb3b-A6QAc8

[2]https://www.nasa.gov/earth-and-climate/human-activities-are-...

[3]https://www.rainforesttrust.org

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1. woah ◴[27 Sep 25 21:07 UTC] No.45399309[source]▶
> The reason for this is that it is a leftover from when the planet was covered in rainforests because it was a lot warmer and wetter in the Eocene epoch.

Won't it get much warmer and wetter once global warming hits, allowing the rainforest to grow back?

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2. XorNot ◴[27 Sep 25 21:37 UTC] No.45399529[source]▶
Global warming will not reforest the planet with a substantially different biosphere to set the conditions for the Amazon to regrow and then persist.

I mean I suppose it could but contingent on that would be things like "thousands of years" and "likely substantial extinction of human population centers".

3. TSiege ◴[27 Sep 25 21:40 UTC] No.45399558[source]▶
Not necessarily, (or even according to climate models I’ve seen). The feedback the OP mentioned is because trees near the coasts catch rain that they then respirate back up and create an atmospheric river that moves inland and falls as rain thus continuing the cycle inward. This cycle is disrupted by deforestation and can stop during a state change where it turns into Savannah. Savannah's are much drier and don’t cycle through water like the rain forest would. We’ll also see abrupt changes in global climate which will lead to completely different global rainfall patterns than we know today. For example the Sahara desert will likely turn into grassland/forest (which has happened in the past). The rainforest being a holdover from the Eocene is news to me, but my understanding was that the climate of the Holocene that we are leaving had weather patterns that facilitated a positive feedback with the Amazon rainforest expansion. From my understanding a thriving Amazon also necessarily depended on a desert Sahara as they drive weather/nutrient patterns that helps the Amazon
4. ◴[27 Sep 25 21:42 UTC] No.45399571[source]▶
5. blueflow ◴[27 Sep 25 21:44 UTC] No.45399592[source]▶
Eocene temperatures: 6-15 kelvin above current. Would take another century or two of coal-burning to reach.
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6. ghm2199 ◴[27 Sep 25 21:44 UTC] No.45399595[source]▶
Without the trees, more rain may erode the soil, the Amazon river might flood more easily causing more erosion.
7. TSiege ◴[27 Sep 25 21:49 UTC] No.45399634[source]▶
We are already at Eocene levels of CO2 it’s just that our climate hasn’t caught up yet
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8. blueflow ◴[28 Sep 25 09:40 UTC] No.45403049{3}[source]▶
I think that's wrong, Eocene ended when levels had fallen to roughly 600-700 ppm? And we are at 480 ppm now.
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9. TSiege ◴[09 Oct 25 19:05 UTC] No.45531736{4}[source]▶
You are correct. I meant the Miocene where towards the end CO2 was ~500 ppm which we are over with CO2e.